In order to conserve the amount of surface area, or “real-estate,” consumed by integrated circuits on a carrier substrate, such as a circuit board, various types of increased density packages have been developed. Among these types of increased density packages is the so-called “multi-chip module” (MCM). Some types of multi-chip modules include assemblies of integrated circuits that are stacked one on top of another. The amount of surface area on a carrier substrate that may be saved by stacking integrated circuits is readily apparent.
The system of increasing semiconductor density on a circuit board by stacking semiconductor packaged devices one on top of another is commonly referred to a “package to package” or a “package on package” assembly. One problem with the current package to package system assembly is difficulties caused by irregularities in the flatness/coplanarity of the lower package. Another problem results from the increased stiffness of the overall assembly, which can lead to reduced board level reliability. Still another problem can arise from poor heat dissipation from the upper package.
The typical package on package stacked semiconductor assembly uses an interposer structure between the first package and the second package. A second package fits mounts onto an interposer substrate using a ball grid array (BGA) interface. The interposer substrate provides electrical contact points at the peripheral boundary. The second package electrically couples to the first substrate through the ball grid array (BGA) interface through the interposer substrate then connected to the first substrate. This packaging system and design requires additional interposer structure and manufacturing steps to create the package on package assembly with degraded electrical performance.
Thus, a need still remains for a package on package (POP) semiconductor package with a stacking substrate assembly to stack the multiple packages without intermediate structures, such as an interposer. In view of the ever-increasing need to save cost and improve efficiencies, it is increasingly critical that answers be found to these problems.
Solutions to these problems have been long sought but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art.